In the production of a usable gas by the combustion of a carbonaceous fuel, the process is operated most effectively in a gasifier or reactor under high temperature and high pressure conditions. For example, for the efficient production of a synthesis gas from a particulated coal or coke, a preferred operating temperature range of about 2400.degree. to 2600.degree. F. is maintained, at a pressure of between about 5 to 250 atmospheres.
The harsh operating conditions prevalent in such a method, and in particular the wide temperature variations experienced, imposes a severe strain on many segments of the gasifier or reactor unit. A reactor of this type is normally furnished with thermal insulation as well as with a system to cool interior parts. Usually such parts as the dip tube that contacts the hot effluent gases, must have adequate cooling if the usable life of this member is to be preserved.
The present invention is addressed to an improvement in the structure of a gasifier, and particularly in the gasifier's quench ring and cooling water distribution system including the cooling water distribution manifold. The latter, by its inherent function, is exposed to maximum temperature conditions and destructive gases. This occurs by virtue of the hot synthesis gas which comes in direct contact with the quench ring and manifold as the hot effluent passes from the combustion chamber, into a cooling or quenching zone.
In the usual reactor structure, the combustion chamber within the reactor shell is lined with a refractory material to avoid thermal damage to the shell. This refractory material can take the form of individual bricks or it can be in the configuration of a unitary member shaped of a castable refractory material. In either instance, the refractory blocks or members are combined and shaped to define the gasifier's constricted throat.
The refractory throat members are normally supported in a way that they can be removed if required for repair or replacement. One form of support resides in placing the quench ring in such a position that it will support the throat from the underside. Thus, the quench ring, which is fastened to the shell wall, will locate the supported throat.
However, during a shut down period, it is probable that in the course of normal cooling, metallic segments of the gasifier such as the quench ring and its auxiliary parts will cool rapidly. This will allow quick access to the reactor interior for performing necessary repair or maintenance work.
Where the reactor's quench ring requires removal from the gasifier for repair or replacement, it is necessary to first detach the refractory blocks which make up the constricted throat. These non-metallic members take a much longer period of time to cool down than does the metallic quench ring. Thus as a practical matter, it can be several days before one can obtain safe access to the reactor interior to permit removal of the quench ring. Furthermore, removal of the throat refractory necessitates the expense of its replacement. This follows, since used fire brick, once disturbed, cannot be reassembled correctly.
In the instance of the gasifier dip tube, this member is exposed to the harsh conditions in the normal course of operating. Even though the dip tube guide surface is wetted by a coolant stream, the dip tube is still subject to thermal damage after a period of time. This results not only from the contact between the flowing gas and the dip tube surface, but also due to the thermal stresses.
Toward overcoming these persistent operating problems, and to minimize gasifier down time and throat replacement, the present invention embodies a gasifier structure wherein the constricted throat between the combustion chamber and the quench chamber is formed of one or more refractory blocks. The latter are supported in place by a quench ring having a separable manifold section. Thus, when the exposed hot face of the dip tube assembly is damaged to the point of needing repair, it can be readily removed without disturbing the quench ring which remains in place supporting the refractory throat.
The water carrying manifold section which maintains a coolant stream against the reactor's dip tube, is detachably fixed to the water conducting quench ring. In a preferred construction, the respective manifold and quench ring, are provided with a thermally resistant gasket compressed between mating surfaces to minimize the flow of heat therebetween. Thus, the refractory member or members which define the constricted throat need not be disturbed when the manifold is removed. Further, the thermally resistant gasket between the mating or engaged members minimizes heat transfer therebetween.
To facilitate and protect the dip tube, the latter is provided with a liquid flow, normally a stream of water. This flow wets the interior surface of the tube thereby affording it a substantial degree of protection from the hot gaseous effluent which often carries solid particulate matter. To improve the flow of water from the quench ring onto the dip tube assembly, from whence it is directed against the dip tube surface, the dip tube is provided with a jacket. Said jacket functions as an intermediary or surge chamber for the liquid prior to its passing into the distribution ring or channel. In the latter, the liquid functions to cool or transfer heat from the normally hot face of the exposed member, thereby minimizing the thermal damage to portions of the quench ring.
In terms of economics, the cooperative arrangement of the quench ring and the dip tube assembly, permits the latter to be completely removed while leaving the supporting ring in place. Shut down time of the gasifier can therefore be reduced by several days through use of the disclosed separable quench ring and cooled dip tube arrangement. Thus, the quench ring is adapted to removably receive the dip tube assembly which is comprised basically of the dip tube guide surface as well as a water distribution channel.
It is therefore an object of the invention to provide an improved gasification reactor having a jacketed dip tube assembly for guiding hot effluent from the reactor's combustion chamber into the liquid cooling bath.
A further object is to provide a dip tube assembly that is readily detachable from a quench ring to facilitate access to the reactor's interior.
A still further object is to provide an improved dip tube cooling system for a gasifier reactor by providing a surge chamber about the dip tube thereby to decrease the possibility of thermal damage thereto.
Another object is to provide a multi-segmented quench ring for a gasification reactor, which can be disassembled and removed piecemeal from the refractory's interior.